In this section we review the two models that we use - the SYK Majorana fermion [1]}, [2]}, [3]} and the Pauli matrices model [4]}, [5]}, [6]}. We will be interested in the case of the two sided black hole and hence the space is doubled. We will then review the chord diagram techniques for these models, in the double scaling limit. Our main conceptual points do not rely on the double scaling limit, but it will be useful computationally.
